Conventionally, a film drying device used in a film production process is a film drying device in which a film is dried by putting the film in contact with art outer peripheral surface of a heated cylindrical roller.
In association with the above-described technique, there is a known drying roller device in which a heating medium fluid is circulated inside a cylindrical member, so that a sheet-like heat-treatment target object in contact with an outer peripheral surface of the cylindrical member is heated to a predetermined temperature to dry (Patent Literature 1). In the drying roller device, the heating medium fluid is provided for the purpose of making the temperature of the outer peripheral surface of the cylindrical member uniform, which cylindrical member constitutes a main body of a drying roller. This heating medium fluid is caused to flow into the cylindrical member through a flow path, which is provided through a core cylinder located in a space formed inside the cylindrical member, and then to flow out of the cylindrical member after passing through another flow path between an inner peripheral wall of the cylindrical member and an outer peripheral wall of the core cylinder.
Meanwhile, there is a drying roller device that heats a film wrapped, in such a manner that a certain level of tension on the film is maintained, around outer peripheral surfaces of a plurality of cylindrical members through each of which a heating medium is caused to flow helically (Patent Literature 2). This device is provided with ducts in a multiple helical arrangement inside each of the cylindrical members so that the heating medium may pass through one end surface to the other end surface of the cylindrical member. Then, a film is put in contact with the outer peripheral surfaces of the plurality of cylindrical members, so that a certain level of tension on the film will foe maintained.